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Copyright: 1996 - 2024 Webmaster:
Kirt Blattenberger,
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
My Hobby Website:
AirplanesAndRockets.com
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Thermocouples |
Thermocouples work on the
Seebeck principle, discovered accidentally in 1822 by an Estonian physician named Thomas Seebeck. Basically, the
Seebeck principle explains how two dissimilar metals generate a temperature-dependent flow of current at their
welded junction when attached to a closed circuit.
Seebeck discovered that a compass needle would be
deflected when a closed loop was formed of two metals joined in two places with a temperature difference between
the junctions. The metals respond to temperature by assuming different voltage potentials, thereby generating a
current related to the temperature of the junction.
This table lists the properties of the most
common thermocouple junctions.
B |
Platinum30% Rhodium (+) Platinum 6% Rhodium (-)
|
Gray Red |
0 to 13.820 |
0 to 1700°C (32 to 3092°F) |
C |
W5Re Tungsten 5% Rhenium (+) W26Re Tungsten 26% Rhenium (-)
|
White Red |
0 to 37.066 |
0 to 2320°C (32 to 4208°F) |
E |
Chromel (+) Constantan (-)
|
Violet Red |
-9.835 to 76.373 |
-200 to 900°C (-328 to 1652°F) |
G |
Tungsten 26% (+) Rhenium W-26% (-)
|
White Red |
0 to 38.564 |
0 to 2320°C (32 to 4208°F) |
J |
Iron (+) Constantan (-)
|
White Red |
-8.095 to 69.553 |
0 to 750°C (32 to 1382°F) |
K |
Chromel (+) Alumel (-)
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Yellow Red |
-6.458 to 54.886 |
-200 to 1250°C (-328 to 2282°F) |
N |
Nicrosil (+) Nisil (-)
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Orange Red |
-4.345 to 47.513 |
270 to 1300°C (-450 to 2372°F) |
R |
Platinum 13% Rhodium (+) Platinum (-)
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Black Red |
-0.226 to 21.101 |
0 to 1450°C (32 to 2642°F) |
S |
Platinum 10% Rhodium (+) Platinum (-)
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Black Red |
-0.236 to 18.693 |
0 to 1450°C (32 to 2642°F) |
T |
Copper (+) Constantan (-)
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Blue Red |
-6.528 to 20.872 |
-200 to 350°C (-328 to 662°F) |
Thermocouple types R, S, and B are constructed of platinum and rhodium, and are referred to as noble metal
thermocouples. They are more accurate and more stable than base metal types, but are more expensive.
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